<!DOCTYPE html>
<html   xmlns="http://www.w3c.org/1999/xhtml"
        xmlns:h="http://java.sun.com/jsf/html"
        xmlns:p="http://primefaces.org/ui"
        xmlns:f="http://xmlns.jcp.org/jsf/core">
    <h:head/>
    <h:body>
        <p:panel id="pnl" header="My Panel">
        //content
        <p:commandButton id="saveBtn" value="Save" />
        </p:panel>
        <p:panel id="pnl2" header="My Panel">
        //content
        <p:commandButton id="lalalaBtn" value="Lalala" />
        <p:commandButton id="lululuBtn" value="Lululu" />
        </p:panel>
        <p:blockUI block="pnl2" trigger="saveBtn">
            LOADING...<br />
            <p:graphicImage value="IMG/ajaxloading.gif"/>
        </p:blockUI>
    </h:body>
</html>